The invention set forth and claimed in this specification pertains to new and improved tubing such as is preferably used for irrigation purposes which will lay flat when coiled and which will automatically expand to a normal configuration as it is used.
Although a number of different types of tubing are currently used for irrigation purposes it is believed that the vast majority of such tubing is common seamless cylindrical tubing formed by extruding an organic polymer or polymer mixture which is flexible when present in a comparatively thin panel or wall but which is substantially inflexible when present in a wall or panel of significantly greater thickness. Such tubing is comparatively inexpensive and can be formed of a composition which is relatively immune to deterioration under normal conditions of use in a field or the like. Many of such polymer compositions are of such a character that comparatively limited amounts of polymer material are required in a tube which can be used with water or other liquid at a moderately high pressure without significant danger of the tube rupturing.
Even though such cylindrical tubing is advantageous for irrigation and other uses it is considered to be less desirable than desired from an economic standpoint because the shape of the tubing effectively precludes it from being coiled and otherwise handled as easily flat, bendable ribbons or strips of various materials can be coiled and handled. This is best illustrated by discussing two different types of such cylindrical tubing--formed out of a material which is of a limited flexibility and tubing formed of a material which is relatively flexible.
Cylindrical tubes formed of a material having such limited flexibility frequently do not collapse to a relatively flat configuration or can only be collapsed to such a configuration with difficulty. It is well recognized that it is frequently difficult or impossible to wind such tubing into a "tight" coil having a relatively small diameter. It is also commonly known that when such relatively inflexible tubing is wound onto a coil that the coil contains a great deal of air because the tubing in it is not flat or relatively flat but is essentially "open". As a consequence of this it takes more space to store coils of relatively inflexible tubing than may be desirable.
As opposed to this comparatively flexible thin walled tubing can be flattened so as to be more easily coiled into a comparatively "tight" coil of a relatively small diameter. Unfortunately there is a significant possibility of such tubing being damaged if it is improperly manipulated as it is flattened or if it is formed of a material of lesser flexibility than necessary to withstand a flattening operation. Also it is unfortunate that the amount to which such tubing can be flattened is limited by the fact that the edges of the flattened tubing normally will be shaped more or less like loops and will contain small internal spaces paralleling such edges. Efforts to remove these edge "loops" by the use or pressure on the tubing are considered to be undesirable because of the possibility of damaging the tubing walls adjacent to such loops.
As a result of these and other considerations it is believed that there is a need in at least the irrigation or plat watering fields for new and improved tubes or tubing which are capable of being flattened for coiling and storage purposes and which are capable of being expanded to a normal cross-sectional configuration without any loss of intended physical properties. This latter is considered important. Many of the polymers and polymer compositions useful in forming tubing are of such flexibility that they can only be bent or flexed to a limited extent without the danger of damage.